Molecular design and synthesis of narrow-bandgap poly(thienylenevinylene)s via Co‐catalyzed hydroarylation polyaddition

Donor–acceptor conjugated polymers have been designed and synthesized to develop high-performance organic semiconductors. In this study, the site- and regioselective synthesis of narrow-bandgap poly(thienylenevinylene)s (PTVs) is demonstrated via Co-catalyzed hydroarylation polyaddition of 4-amidethiophene derivatives. The hydroarylation polyaddition of four types of thiophene-based aromatic monomers with 3,6-bis(5-ethynylthiophene-2-yl)-2,5-dialkyl-pyrrolo[3,4-c]pyrrole-1,4-dione yields the corresponding PTVs and does not produce byproducts from the monomers. The high planarity of the thienylenevinylene backbone extends the effective conjugation lengths, thereby narrowing the optical bandgap of the PTVs. Furthermore, the lowest unoccupied molecular orbital energy levels are deepened because of the introduction of electron-accepting building blocks, as measured by performing low-energy inverse photoelectron spectroscopy (LEIPS). The obtained PTV has a narrow band gap and a deep LUMO energy level. The properties are appropriate for the non-fullerene acceptor for organic photovoltaics, serving as an n-type semiconducting material.